Ask a physicist anything. (2)

[canehdianhotstuff]

Opposite spinning paired electrons, or same spinning electrons. Cause a spin-paired set of electrons, let's say H atoms, will attract eachother over infinite distance. Van der Waals forces.

 

[AV1611VET]

Well, not exactly. If the universe only contained two electrons, then smack bang in the middle there would be zero gravity, both in terms of the warping of spacetime and in terms of the force felt by a particle there.

I disagree, but I'm not sure why.

Are you saying that a particle in the center of the universe would have zero gravity because the force of gravity from the electrons are canceling each other at that point?

 

[Wiccan_Child]

I disagree, but I'm not sure why.

Are you saying that a particle in the center of the universe would have zero gravity because the force of gravity from the electrons are canceling each other?

Yep. Though the two electrons are attracted to the middle, the central electron would feel nothing. Of course, this only works if the central electron is in the very centre of the system.

It's the same idea that means someone in the centre of the Earth would be weightless.

 

[Wiccan_Child]

Opposite spinning paired electrons, or same spinning electrons. Cause a spin-paired set of electrons, let's say H atoms, will attract eachother over infinite distance. Van der Waals forces.

We're only talking about gravity, not electromagnetism. And I doubt you could get charge coupling of any significance over large distances.

 

[Tinker Grey]

We're only talking about gravity, not electromagnetism. And I doubt you could get charge coupling of any significance over large distances.

Hawking suggests (as I understand it) in A Brief History of Time that the stronger the force the more limited the effect. Gravity is the weakest, but is felt across the universe (e.g., the milky-way and Andromeda are due to collide in 5 billion years due to gravity, IIRC). The strong nuclear force is the most intense but is comparatively limited.

Is this your understanding?

 

[canehdianhotstuff]

Well true over a great distance they are unaware of each other. But as long as temp. is above absolute zero random movement exist. They wander till they become close enough that although weak, Van der Waals forces take hold. Once initiated is becomes strong enough till the 2 orbitals combine.

 

[AV1611VET]

Yep. Though the two electrons are attracted to the middle, the central electron would feel nothing. Of course, this only works if the central electron is in the very centre of the system.

Then zero gravity is only theoretical, is it not?

Since it would only work in a universe that has two electrons, and this universe is not structured that way, zero gravity doesn't exist --- only on paper.

 

[Cabal]

Well true over a great distance they are unaware of each other. But as long as temp. is above absolute zero random movement exist. They wander till they become close enough that although weak, Van der Waals forces take hold. Once initiated is becomes strong enough till the 2 orbitals combine.

I'm curious as to why you brought up vDW forces? vDW is a charge interaction, not gravitational, and even then falls away faster than the Coulomb interaction. And this would only have an indirect effect on any other particle present in the interaction.

 

[Cabal]

Hawking suggests (as I understand it) in A Brief History of Time that the stronger the force the more limited the effect. Gravity is the weakest, but is felt across the universe (e.g., the milky-way and Andromeda are due to collide in 5 billion years due to gravity, IIRC). The strong nuclear force is the most intense but is comparatively limited.

Is this your understanding?

Not necessarily - electromagnetism has the same range of gravity (infinity) but is a much stronger interaction.

But yes, the long ranged forces are not such strong interactions as the strong force.

 

[Cabal]

Then zero gravity is only theoretical, is it not?

Since it would only work in a universe that has two electrons, and this universe is not structured that way, zero gravity doesn't exist --- only on paper.

Given the weakness of gravity and how quickly that effect falls away over distance, microgravity can be considered to be effectively zero gravity.

 

[AV1611VET]

Given the weakness of gravity and how quickly that effect falls away over distance, microgravity can be considered to be effectively zero gravity.

Then WC's two-electron paradigm is wrong?

And I have a feeling you aren't, but are you suggesting that the force of gravity is limited with regard to distance?

 

[Cabal]

Then WC's two-electron paradigm is wrong?

Not wrong. Just approximable. A femtometer /s^2 acceleration is peanuts on the scale of something big like a spacecraft.

And I have a feeling you aren't, but are you suggesting that the force of gravity is limited with regard to distance?

Again, not limited, but over very large distances it falls to such low levels it may as well be zero, and the interaction times become impracticably large.

 

[AV1611VET]

Again, not limited, but over very large distances it falls to such low levels it may as well be zero, and the interaction times become impracticably large.

Well ... since zero has its own value ... I'll go with what scientists call it.

Better yet --- let's look at it this way:

At the quantum level, there is no such thing as zero gravity.

How's that?

 

[Cabal]

Well ... since zero has its own value ... I'll go with what scientists call it.

Better yet --- let's look at it this way:

At the quantum level, there is no such thing as zero gravity.

How's that?

Eh, not so great, I'm afraid. We don't even know how gravity works on the quantum level. Besides, it's not really so much of a quantum issue per se, you just need to compare the magnitude of the force over the timescales and length scales of the behaviour of the object you're looking at. If you're talking about femtometers of motion of something a few hundred metres long on a short timescale then there is in practice little different between calling it stationary and giving it an acceleration so small you probably won't even get to observe it happening.

 

[Wiccan_Child]

Hawking suggests (as I understand it) in A Brief History of Time that the stronger the force the more limited the effect. Gravity is the weakest, but is felt across the universe (e.g., the milky-way and Andromeda are due to collide in 5 billion years due to gravity, IIRC). The strong nuclear force is the most intense but is comparatively limited.

Is this your understanding?

I don't think one necessarily follows the other; I don't see why we couldn't have a very strong force that has such wide effects as gravity. Obviously, we don't, but I don't think there must necessarily be a trade-off.

Well true over a great distance they are unaware of each other. But as long as temp. is above absolute zero random movement exist. They wander till they become close enough that although weak, Van der Waals forces take hold. Once initiated is becomes strong enough till the 2 orbitals combine.

Again, we're talking about lone electrons. There are no orbitals to combine.

Then zero gravity is only theoretical, is it not?

Since it would only work in a universe that has two electrons, and this universe is not structured that way, zero gravity doesn't exist --- only on paper.

On the contrary, there are points dotted about the universe that just so happen to have a net zero gravitational field. For whatever reason, at that point, the gravitational fields just so happen to add up to zero. They're obviously rare, and they will move about as objects in space move about. But they exist, nonetheless.

To a good degree of accuracy, Lagrange points are examples of these. These are the places where the Earth's and Sun's gravity cancel each other out:

 

[Wiccan_Child]

Then WC's two-electron paradigm is wrong?

And I have a feeling you aren't, but are you suggesting that the force of gravity is limited with regard to distance?

The gravitational force felt by our two electrons will be absolutely tiny, given the distances involved and the minuscule mass each electron has. In the real world, other forces will completely drown out the electron's gravitational field, but in our hypothetical, there's nothing to drown it out.

 

[Cabal]

On the contrary, there are points dotted about the universe that just so happen to have a net zero gravitational field. For whatever reason, at that point, the gravitational fields just so happen to add up to zero. They're obviously rare, and they will move about as objects in space move about. But they exist, nonetheless.

To a good degree of accuracy, Lagrange points are examples of these. These are the places where the Earth's and Sun's gravity cancel each other out:

While Lagrange points kick backside, I suspect this won't be counted as a zero gravity point by certain individuals, because of all the other mass in the universe. Even though they're too far away to make a difference and one could effectively consider their contribution to be isotropic and thus zero anyway.....

 

[AV1611VET]

If you're talking about femtometers of motion of something a few hundred metres long on a short timescale then there is in practice little different between calling it stationary and giving it an acceleration so small you probably won't even get to observe it happening.

I'm sure that's why it's prefaced by, "micro-".

For the sake of attenuation though, I'll consider both of our points valid ones.

How's that?

 

[Wiccan_Child]

While Lagrange points kick backside, I suspect this won't be counted as a zero gravity point by certain individuals, because of all the other mass in the universe. Even though they're too far away to make a difference and one could effectively consider their contribution to be isotropic and thus zero anyway.....

Hence why I said "to a good degree of accuracy" . And besides, the true system is a very good approximation of the idealised case.

 

[AV1611VET]

The gravitational force felt by our two electrons will be absolutely tiny, given the distances involved and the minuscule mass each electron has. In the real world, other forces will completely drown out the electron's gravitational field, but in our hypothetical, there's nothing to drown it out.

"Zero gravity" is a term that is one vote away from being plutoed ---